If a traveler on a sinful journey lacks water, must he perform Tayammum (dry ablution)?
Chapter on the Traveler's Prayer
Al-Mughni
Book of Prayer
Primary text
If the sinner lacking water during his journey intends to pray, he must perform Tayammum. Prayer remains obligatory, and purity for it is also obligatory, thus the ruling to perform Tayammum becomes a firm obligation (Azimah) in this circumstance.
Supporting text
There are two opinions regarding whether this person must repeat the prayer later. The preferred opinion states that no repetition is required because he performed what was commanded of him, namely the Tayammum and the prayer, and Tayammum in this instance functions as a firm obligation, unlike dispensations, which are optional. The second opinion suggests repetition is required because this ruling (Tayammum) is a matter related to travel, similar to other travel dispensations.